Foams and foamed articles often find utility in acoustic systems for sound absorption and insulation. Such foams, when developed for different market segments (appliance, automotive, industrial, building and construction, etc) often need to meet certain acoustic performance requirements and there is also a desire to add certain particulate additives to foams to obtain certain desired properties. An example of such particulate additives are fire retardants and fire retardant adjuvants to meet certain fire-test-response characteristics (ASTM E176).
Unfortunately, the typical particulate additives, when added to the polymer resin formulation, often cause a number of problems during the manufacture of the foam that have an adverse affect on obtaining acoustically active macrocellular foams. They often act as nucleating agents in the foaming process and provide additional nucleation sites, resulting in the formation of a large number of small cells with variable properties. Unfortunately, foams having an average cell size less than 1.5 millimeter (mm) are often not as desirable as foams having a larger average cell size in certain end use applications, such as acoustic absorption.
U.S. Pat. No. 4,277,569 teaches the preparation of flame retardant polyolefin foams for thermal insulation and padding. However, that patent does not describe macrocellular foams or flame retardant macrocellular foams for acoustic applications or their preparation.
Japanese Laid Open Patent Application No. 10-204200 describes olefin resin foams for use in vacuum molding made from 100 parts by weight of an olefin type resin comprising 30 to 90 percent by weight propylene type resin and 70 to 10 percent by weight ethylene type resin, 1 to 100 parts by weight of a brominated compound and 0.1 to 10 parts by weight of antimony trioxide having an average particle size of 0.4 microns or smaller. Macrocellular foams useful for acoustic applications are not described.
WO 00/15697 describes a macrocellular acoustically active foam which may be surface treated with a solution containing certain fire retardant materials. While that procedure is able to confer fire retardancy, it requires the extra steps of treating the foam after extrusion and perforation and then drying the foam to remove the liquid media used to apply the fire retardant.
Therefore, a significant market need still exists for a large cell, acoustically active foam containing particulate additives. This need is not only generally applicable to polymer foams, but is also particularly acute in the area of thermoplastic foams (that is, foams that are substantially uncrosslinked and capable of being remelted) and foams that also resist water absorption such that they may be used in humid or wet environments without losing performance or potentiating corrosion or microbial growth problems. These, and other problems as described below, are solved by the present invention.